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Discussion Starter #1
After purchasing a Geissele Automatics Suppressor Alignment Rod, for 5.56 mm we checked all my friends 5.56 AR's for proper suppressor alignment. Upon checking them, we found the Colt, Knights, and LWRC barrels allowed the suppressor alignment rod to freely and easily slide through the barrel from breech to bore with no friction. However, the Daniel Defense 12.5 inch barrel didn't allow the gauge rod to freely pass through the barrel. A slight nudge was needed to push the gauge rod through the barrel. It showed a partial fail for suppressor alignment. We believe the Gemtech G5 T flash hider needs adjusting, suspected misaligned shim, but the question remains, why doesn't the rod pass through freely. Aren't all mil spec barrels diameters the same ? The Daniel Defense rifle shoots fine, as do all the others. There is about 650 rounds through this barrel. The other rifles mentioned that we checked all have 14.5 and 14.7 inch barrels. Is the shorter 12.5 inch Daniel Defense barrel supposed to have tighter diameter because of a slightly shorter barrel length...I wouldn't think it would, but this is what brings us to this mighty forum....looking for some input if anyone can explain this quagmire.
 

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We believe the Gemtech G5 T flash hider needs adjusting, suspected misaligned shim, but the question remains, why doesn't the rod pass through freely. Aren't all mil spec barrels diameters the same?
Not understanding the "misaligned shim" ... G5-T FH/mount only requires the washers/shims on the 10.3/10.5 MK18 barrels? You shouldn't need them on the 12.5, unless handguard clearance is an issue? If not, the mount should be snugged up against the thread shoulder to insure bore-to-shoulder are perpendicular. Regardless, indexing shims can't really affect bore-to-shoulder alignment, unless the shim thickness is way out of spec. Try dropping the alignment rod through with the muzzle device removed to confirm whether it's definitely the bore that's tight. DD makes a damn good barrel but it's possible that it's a slightly tight bore. I wouldn't be too concerned about it since you can get the alignment rod through with a nudge ... it'd take more than that to cause a baffle strike.
 

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Discussion Starter #4
Interesting note about the shims/washers on 12.5 barrels. It's definitely shimmed. We had a local gun smith attach it for us. He is very reputable but we've had some minor mishaps and mistakes on some relatively easy tasks we have brought to him due to lack of tools to do some minor jobs. I agree that's probably not the issue any way, as yes, it would have to be a pretty big defect in the washer to cause misalignment. The alignment rod stops free floating through the barrel well before it reaches the flash hider though. We thought of the threading for the flash hider being slightly off, and that's possible I guess. But the chrome lining process of a barrel is known to be a tough process to get just right. The chances of crooked threading on the end of the barrel, and an imperfected chrome lining wouldn't be astronomical I guess, but in all probability not the case. Daniel Defense does make fine barrels. If they simply made tighter tolerances throughout their barrel, the alignment rod should still exit the breech straight. At the end of the day, this is a Daniel Defense question I believe. We've shot off an email to them and will wait for their reply after this weekend. I personally think it's going to be a slight imperfection/high spot on the chrome lining of the barrel. But accuracy is excellent out of this rifle, and it seems if there was a chrome lining issue we would see an accuracy problem...I don't really know. I think it's minor either way, and may be fine just left alone. But showing a partial fail raises concern over the possibility of a baffle strike. I'm guessing a few hundred rounds through it suppressed without a problem so far though. But you can understand the concern when we saw partial fail register. I don't think the concern level would be so bothersome if it weren't such a long process for obtaining suppressors...another thread to itself lol. Thanks for the input guys, I'll keep you posted as to our findings, and what Daniel Defense says.
 

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I believe Daniel Defense barrels have a tapper from the breech to the muzzle, which would account for the Suppressor Alignment Rod not freely traveling through the barrel. I believe HK MR556 has a similar tapper in their barrel.
Regarding the partial fail while using the Suppressor Alignment Rod, there could be some slight damage to the end of the barrel which could cause this. A competent gun smith should be able to take care of this issue.
 
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